Security in Computing 5th Edition by Shari Lawrence Pfleeger, Charles P Pfleeger, Jonathan Margulies

Exercise 6

(a) If passwords are three uppercase alphabetic characters long, how how much time would it take to determine a particular password, assuming that testing an individual password requires 5 seconds?

(b) Argue for a particular amount of time as the starting point for “secure.” That is, suppose an attacker plans to use a brute force attack to determine a password. For what value of x (the total amount of time to try as many passwords as necessary) would the attacker find this attack prohibitively long?

(c) If the cutoff between “insecure” and “secure” were x amount of time, how long would a secure password have to be? State and justify your assumptions regarding the character set from which the password is selected and the amount of time required to test a single password.

Step 1 of 3

a) The password to be generated has 3 characters to decode. There are 26 alphabets, so for 1 as password length, possible password is. For a password with 2 as character length, number of possible password is. So a password length of 3 will have passwords.

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Thus, the password will take maximum of 24 hours 24minutes and 40seconds to decode.